The present invention relates to wire ties for concrete forms.
Wire ties are used for spacing the panels used in poured concrete forms. The ties provide the correct spacing of the panels and may be used to support reinforcement bars (rebar). When the concrete is set and the form panels are removed, the ends of the ties projecting from the concrete are removed.
The wire ties in common use include the tie disclosed in U.S. Pat. No. 1,692,166 issued Nov. 20, 1928, to L. O. Gates, and U.S. Pat. No. 3,168,912 issued Feb. 9, 1965, to G. E. Marica. The Gates tie has a single wire formed into a three-strand, twisted cable at the center, retainer loops at each end and transverse stops between the retainer loops and the center section.
A tie that is intended to address certain limitations of this prior art tie is disclosed in U.S. Pat. No. 3,722,836 issued Apr. 24, 1973, to R. C. Gates. This tie is a single strand formed into a loop with a single strand on one side, a twisted double strand cable on the other side and return bends at opposite ends as retainer loops. The ends of the wire are formed into rebar saddles on the twisted side of the loop, facing away from the single strand side of the loop. With a tie of this type, sufficient tension applied to the tie will cause the twisted strand to xe2x80x9cunwindxe2x80x9d, stretching the overall length of the tie and allowing the form panels to separate to an unacceptable extent. This tie is not used commonly, if at all.
Another loop type tie that eliminates the twisted side of the loop is disclosed in U.S. design Pat. Des. 300,117 issued Mar. 7, 1989, to H. Gordon Gates. In that tie, one end of the wire strand is crossed over from one side of the loop to the other midway between the ends, and the ends are welded to the respective sides of the loop. It is believed that the welding of the tie should be avoided. These welds are in shear and must be carefully made in order to avoid breakage with consequent failure of the tie. The stops of this tie are on opposite sides of the loop, so that they cannot be used in locating rebar for both sides of a concrete panel to be formed.
The present invention is concerned with the provision of an improved, twisted, loop type tie that is resistant to the unwinding of the prior art, twisted loop tie.
According to the present invention there is provided a wire tie for concrete forms comprising a length of wire having:
a center section formed to provide an elongate loop with:
a first side;
a second side with overlapping strands twisted together; and
reverse bends between the first and second sides of the loop; and
two end sections at opposite ends of the second side of the loop, each end section being formed into an anti-rotation stop extending from a respective end of the twisted second side of the loop and engaging the first side of the loop so as to prevent rotation of the stops relative to the loop.
Bringing the ends of the wire across the loop to engage both sides of the loop in a manner that prevents untwisting of the twisted side overcomes the main difficulty with the prior art tie. This may be achieved by having the stops project from the ends of the twisted second side of the loop on one face of the loop and cross over to engage the first side of the loop on the opposite face of the loop.
In preferred embodiments, the stops are formed into a U-shaped configuration with one arm that projects from the twisted second side of the loop, across the untwisted first side and a second arm that returns across both sides of the loop. This not only provides the stop function of the tie to position the forming panels properly with respect to the tie, it also provides a seat for the positioning of rebar at the intersection of the stop and the untwisted first side of the tie. At least one of the two arms of the U-shaped stops desirably cross over the two sides of the loop on opposite faces of the loop to provide an interlock preventing the unwinding of the twisted side of the loop.